Muffler for intercommunicating system units



April 10, 1945. w. s. DARBY MUFFLER FOR INTERCOMMUNICATING SYSTEM UNITFiled Dec. 27, 1943 g-lg? //A Patented Apr. 10, 1945 UNITED STATES-PATENT OFFICE MUFFLER FOR INTERCOMMUNICATING SYSTEM UNITS 6 Claims.

This invention relates to intercommunicating devices employed in systemswhich permit transmission of two-way conversation between a masterstation and one or more remote sub-stations, and particularly toimprovements avoiding transmission of noise from the remote stations tothe master station.

Systems of the type described are well known in the art and includemicrophone-loud speakers usually enclosed in suitable casings orcabinets at each station. The stations are connected by suitable wiringto transmit electrical currents generated by the impact of sound waveson the transmitter. The microphone-loud speaker permits announcement ofthe message without the necessity for use of a head set or other hearingdevice. It also picks up a message at the substation and transmits it tothe master station.

Frequently it is desirable to provide one or more sub-stations in partsof a plant or factory where a medium or high noise level normallyexists. In such cases the noise is picked up and transmitted, with theresult that the voice sounds are often distorted and thereforeunintelligible.

It is the object of the present invention to pro vide a simple andeffective device whereby extraneous sounds such as the noise ofmachinery and the like can be reduced materially or substantiallyeliminated from the intercommunicating system without interfering withthe facility of use of the system for transmission of conversation.

Other objects and advantages of the invention will be apparent as it isbetter understood by reference to the following specification andaccompanying drawing, in which Fig. 1 is a view in perspective of atypical remote conversational type sub-station;

Fig. 2 is a plan view of a device adapted to be applied to thesub-station for the purpose of the invention;

Fig. 3 is a section on the line 33 of Fig. 2;

Fig. 4 is a section on the line 4-4 of Fig. 2;

Fig. 5 is a view in perspective illustrating a modified form of theinvention;

Fig. 6 is a horizontal section through the device as shown in Fig. 5;and

Fig. 7 is an enlarged view of a spring hinge adapted for use inconnection with the invention.

In carrying out the invention, I employ means adapted to be associatedwith the sub-station to mufile extraneous noise and nevertheless permittransmission of the voice to the microphone-loud speaker. The device isarranged to normally permit conversation transmitted from the central Imanner as for example by hinges I I.

station to be heared without interference. The user may, however, easilymuille the device to prevent the impact of extraneous sounds on themicrophone-loud speaker when he wishes to reply to any message received.In a simple form of the device, it may be attached directly to the frontof the sub-station. Alternatively the sub-station may be enclosed in asuitable casing embodying the device. In either case, the sub-station isalways ready to receive messages which are audible to persons in thevicinity. It may be adjusted by a simple movement to prevent entrance ofextraneous sounds when a message is to be transmitted from thesub-station.

Referring to the drawing, 5 indicates a typical remote conversationaltype sub-station, the details of which form no part of the presentinvention. It may be provided on its face with openings 6 through whichsounds pass to the internal mechanism including the microphoneloudspeaker (not shown). Devices of the type described are in common use andare provided in various forms. The invention is applicable to any suchdevices which are being manufactured and sold for intercommunicatinguse.

Referring to Fig. 2, I provide a cover 1 which is adapted to be securedby means of screws 8'or other suitable means to the face of thesub-station 5. An opening 9 in the cover is adapted to be closed by adoor In supported in any suitable The hinges are preferably of thespring type illustrated in Fig. 7, the springs l2 being adapted to holdthe door In normally in open position. In that position, the face of thesub-station 5 is exposed and sounds produced thereby may be readilyheard by persons in the vicinity. Any other con- 'venient means formaintaining the door in open position may be employed. The edges [3 ofthe door 10 are preferably beveled to afford a more soundproof jointwhen the door is closed, but this is not essential to the invention.

Near the center of the door I provide an opening 14, and on the facethereof I mount a flared speaking tube [5. The opening l4 may beapproximately one inch in diameter, although the precise size is notimportant. An opening of the size indicated will permit voice sounds toenter without muflling So that the message can be picked up by themicrophone-loud speaker and transmitted to the central station. To avoidpickup of extraneous sounds, the user simply pushes the door It) to itsclosed position and holds it there while he is transmitting a message.As soon as the door is released, it will return to its open position sothat any message from the central station can be heard readily.

The cover 1 and the door l may be made'of plywood or any other suitablematerial. It may be provided with additional sound insulating materialif desired, but usually no further insulation is necessary to eliminatethe extraneous sounds from the system when the door I0 is closed.

Referringto Figs. 5 and 6, the sub-station 5 is indicated as whollyenclosed within a casing l6 of wood or other suitable material which mayhave an open bottom so that it is merely dropped over the sub-station.The casing I6 is provided with an opening IT in its face which isadapted to be closed by a door l8 mounted on hinges [9 similar to thehinges shown in Fig. 7. The door i8 is provided with a speaking tube '20which communicates through an opening in the door as in the precedingembodiment of the invention, with the interior of the casing is andhence with the sub-station which will pick up voice sounds when the dooris closed without interference by extraneous noise. When the door I8 isreleased it will swing open so that messages from the central stationcan be heard readily.

The precise detail as set forth are not essential. The inventioncomprehends the provision of a mufiling device which is normally openand may be closed to prevent access of extraneous sounds to themicrophone-loud speaker while per-- mitting voice sounds to betransmitted thereto. Other embodiments of the device adapted toaccomplish the purpose of the invention and having the essentialcharacteristics thereof may be utilized.

Various changes may be made, therefore, in the details of .the devicewithout departing from the invention or sacrificing the advantagesthereof.

I claim:

1. In a communicating system of the type employing a master station anda sub-station, the latter having a microphone-loud speaker to transmitand receive conversation, the improvement consisting of means normallyopen to avoid interference with messages received and adapted to bemanually closed to prevent access of extraneous sounds to themicrophone-loud speaker, such means having an aperture with'a mouthpiececonnected thereto to direct voice sounds to the microphone-loud speakerwhen said means is closed.

2. In a communicating system of the type employing a master station anda sub-station, the latter having. a microphone-loud speaker to transmitand receive conversation, the improvement consisting of a cover for theface of the sub-station having an opening therein, a closure for theopening, means to normally hold the closure in open position to avoidinterference with messages received, the closure having an aperture andav mouthpiece connected thereto ,to direct voice sounds to themicrophone-loudspeaker when the closure is adjusted to close theopening.

3. In a communicating system of the type employing a master station anda sub-station, the latter having a microphone-loud speaker to transmitand receive conversation, the improvement consisting of a cover for theface of the sub-station having an opening therein, a closure for theopening, resilient means to normally hold the closure in open positionto avoid interference with messages received, the closurehaving anaperture and. a mouthpiece connected thereto to direct voice sounds tothe microphone-loud speaker'when the closure is adjusted to close theopening.

4. In a communicating system of the type employing a master station anda sub-station, the latter having a microphone-loud speaker to transmitand receive conversation, the improvement consisting of a casing adaptedto enclose the substation having an opening in the face thereof, aclosure for the opening, means to normally hold the closure in openposition to vaid interference with messages received, the closure havingan aperture and a mouthpiece connected thereto to direct voice sounds tothe microphone-loud speaker when the closure is adjusted to close theopenstation having an opening in the face thereof, aclosure for theopening, resilient means to 'normally hold the closure in open positionto avoid interference with messages received, the closure having anaperture and a mouthpiece connected thereto to direct voice sounds tothe microphoneloud speaker when the closure is adjusted to close theopening.

6. In a communicating system of the type employing master station and asub-station, the latter having a microphone-loud speaker to transmit andreceive conversation, the improvement which comprises a wall in front ofthe microphone-loud speaker having an opening-of relatively large areato permit free egress of sound waves from the microphone-loud speaker tothe atmosphere when messages are being received,

a closure for said opening which is normally open to avoid interferencewith said free egress of the sound waves through said opening butadapted to be manually closed, said closure having an opening ofrelatively small area whereby the closure, when in closed position,obstructs the greater part of the area of said relatively large openingthe prevent access of extraneous sounds to the microphone-loud speaker,and a mouthpiece associated with the small opening in said closure todirect voice sounds to the microphone-loud speaker when the closure isin closed position.

WILLIAM SINKLER DARBY.

